How deforestation drives stream habitat changes and the functional structure of fish assemblages in different tropical regions

1. Deforestation can modify stream habitat and the functional structure of fish assemblages. The aims of this study were (a) to identify whether deforestation has a similar effect on local habitats from two biogeographically distinct river basins in a tropical region; (b) to identify how fish trait–habitat relationships were influenced by deforestation; and (c) to compare functional redundancy patterns in these basins.
2. Environmental and biological variables were obtained for 160 stream reaches, 85 located in the Alto Paraná River basin and 75 in the Machado River basin. Traits were associated with body size, habitat preference, food items and foraging period. Linear models were constructed to verify the environmental convergence of habitats across streams from the Alto Paraná and the Machado basins. An RLQ and a fourth‐corner analysis were conducted to investigate how deforestation affected habitat variables and trait–habitat relationships. The nearest relative index (NRI) was used as a functional redundancy measure.
3. Deforestation led to a similar habitat gradient from streams with a higher proportion of coarse roots in more forested catchments to streams with streamside grasses, bare soil and unconsolidated substrate in more deforested catchments; however, a general pattern of fish trait–habitat relationships was not identified across basins. Functional redundancy was associated with a long history of habitat loss in the Alto Paraná streams, whereas functional complementarity was related to more recent and less intense habitat loss in Machado streams.
4. We believe that differences in regional species pools and historical processes between the basins influenced the fish functional responses to deforestation. Nevertheless, the results highlighted the importance of stream habitat heterogeneity and the presence of preserved forest fragments in a region to prevent the loss of unique traits. Decision‐makers should therefore maintain large forest fragments and restore riparian forests to preserve stream habitat and the functional structure of fish assemblages.

     

Influences of in-stream habitat and upstream land-use on site occupancy of the Kanawha darter (Etheostoma kanawhae): A narrowly distributed species from the New River (Upper Kanawha Basin)

1. Freshwater communities are threatened by the conversion of natural landscapes for urban and agricultural purposes. Changes to land use may disrupt stream nutrient and geomorphological processes and reduce water quality, increase sedimentation, and decrease habitat heterogeneity eventually leading to species loss and decreases in ecosystem productivity. Endemic species are frequently at greater risk of habitat-mediated fragmentation and extirpation due to their constrained distributions.
2. The Kanawha darter (Etheostoma kanawhae) is an understudied fish endemic to the New River Drainage in North Carolina and Virginia, USA. To investigate the potential effect(s) of land-use change on Kanawha darters, naïve occupancy was modelled using instream habitat characteristics and upstream forest cover.
3. Generalized linear models revealed that instream habitat and forest cover are reliable predictors of Kanawha darter site occupancy. Specifically, models demonstrated that occupancy increased in reaches with reduced stream width, velocity, and bedrock substrate but higher concentrations of coarse woody material. Kanawha darter occupancy was also positively associated with the extent of forest cover in upstream catchments.
4. Although Kanawha darters are not currently considered imperilled, most populations occurred in isolated reaches separated by large sections of unoccupied habitat. Continuing ex-urban development in riparian zones is likely to be the primary threat to Kanawha darters and other endemic species in this catchment. Resource managers and stakeholders should preserve forest cover in headwaters and occupied tributaries and protect or restore riparian zones along the main-stem South and North Forks of the New River to preserve high-quality habitat and enhance connectivity among isolated Kanawha darter populations.
5. As human populations in montane regions continue to grow, there is a need to understand how land-use change affects endemic freshwater species. This study further supports the importance of retaining forest cover as an effective strategy for protecting and restoring populations of endemic fishes in high-gradient streams.

     

Changes to freshwater mussel assemblages after 25 years of impoundment and river habitat fragmentation

1. The Tennessee–Tombigbee Waterway is among the largest and most expensive environmental engineering projects of the 20^th century. The waterway accommodates barge navigation between the Tennessee River Drainage and Mobile River Basin through a series of locks, dams, canals, and dredged and diverted streams. These structures have altered riverine habitat and fragmented lotic habitats resulting in isolated freshwater mussel populations in patches of streams such as the East Fork Tombigbee River, where 42 species were known historically.
2. The first post‐waterway mussel surveys in 1987 and 1988 reported 31 taxa. During 2010 and 2011 surveys, 70 sites were sampled using both timed searches and quadrats and detected 29 extant mussel species. Between 1988 and 2010–2011 the relative abundance of nine mussel taxa decreased, whereas the abundance of 11 taxa increased. The populations of three federally listed species were detected at levels below the detection limits in 1988 as well as three non‐native unionids that appear to have colonized the East Fork Tombigbee River via the Tennessee–Tombigbee Waterway River.
3. Although mussel abundance and total species richness were relatively unchanged, assemblage composition shifted toward animals typical of smaller streams rather than large rivers. This shift suggests that present‐day East Fork Tombigbee River habitats favour smaller‐bodied, thinner shelled taxa that are laterally compressed and lack shell sculpture. These taxa are likely to be better adapted to hydrologically and hydraulically variable habitats than are thick‐shelled, large bodied, and sculptured mussels.
4. The results suggest that mussel assemblages are dynamic and may exhibit predictable responses to changes in hydrology, physical habitat conditions, and stream connectivity. However, examinations over broad (20+ yr) temporal scales are needed to observe these shifts. The data demonstrate the value of regular monitoring of diverse mussel assemblages and the importance of stream connectivity and flow modifications to this long‐lived group of benthic invertebrates.

     

Association between burrow densities of two Australian freshwater crayfish (Engaeus sericatus and Geocharax gracilis: Parastacidae) and four riparian land uses

• 1. Freshwater crayfish that burrow into river banks are likely to be affected by riparian land uses that affect soil conditions and vegetation cover. The aim of this research was to determine whether burrow densities of two crayfish species (Engaeus sericatus Clark and Geocharax gracilis Clark) were associated with riparian land use and vegetation type in three streams in south‐west Victoria, Australia.
• 2. Four riparian land‐use categories were studied on each stream: native forest blocks; thin strips of mature native vegetation, fenced, with pasture adjacent; riparian pasture areas, fenced, with no cattle access to the stream; pasture and cattle access to the water's edge. Crayfish burrows were counted and a range of water quality and riparian condition variables were measured.
• 3. Native forest areas were found to have more than twice the densities of freshwater crayfish burrows than other land uses, which did not differ. Native forest areas also had higher mean burrow mound heights but lower burrow activity levels. Riparian characteristics also differed between land uses. In particular, soil compaction was the lowest in native forest areas, which also had better riparian condition scores and water quality than pasture areas.
• 4. This study suggests that cattle grazing may have reduced populations of burrowing crayfish in these streams, and that subsequent fencing and the presence of remnant native vegetation may be insufficient to ameliorate these effects. Blocks of native forest that remain on these streams may act as an important refuge for these species in agricultural areas.

Copyright © 2005 John Wiley & Sons, Ltd.     

Alien and endemic flora at reference and non‐reference sites in Mediterranean‐type streams in Portugal

• 1. A comparison was made between a variety of alien and endemic plant species from 272 aquatic and riparian habitats in Portuguese Mediterranean‐type streams in reference condition — i.e. near‐natural river corridors — and non‐reference condition. The objective was to detect differences in relative proportion and cover between these species groups. The differences in endemic and alien flora from siliceous and calcareous river types were also analysed. Environmental and human disturbance factors were related with the richness and cover of both species groups.
• 2. A total of 568 species were found, of which 44 were alien and 28 were endemic. Alien species were present at 91% of the surveyed locations, and were consistently more widespread at non‐reference sites than at reference ones for both river types, with calcareous sites having a higher invasibility. Endemic species occurred at 45% of the sampling sites and displayed a significantly lower richness and cover than their alien counterparts.
• 3. Alien richness and cover were positively related to direct human disturbance within the river systems, and with floodplain uses such as urban occupation, intensive agriculture, and nutrient inputs. Endemic species also respond to anthropogenic variables, rather than to climatic and geographical ones, with richness and cover increasing as human impacts on fluvial systems and related floodplains decrease.
• 4. Comprehensive control of alien invasive species and the protection of endemic plant populations will require attempts at monitoring ecological river integrity, and the achievement of ‘good ecological status’ — one of the goals of the European Union's Water Framework Directive. Portuguese riparian areas must be managed in such a way as to protect the relatively few preserved riparian habitats by lowering the direct and indirect pressures in fluvial corridors and thus preventing future alien plant invasions.

Copyright © 2006 John Wiley & Sons, Ltd.     

Freshwater mussel assemblage structure in a regulated river in the Lower Mississippi River Alluvial Basin,USA

• 1. This paper documents a diverse, reproducing freshwater mussel community (20 species) in Lower Lake — an impounded, regulated portion of the Little Tallahatchie River below Sardis Dam in Panola Co., Mississippi, USA.
• 2. Despite being regulated and impounded, the lake has a heterogeneous array of habitats that differ markedly in mussel community attributes. Four distinct habitat types were identified based on current velocity and substrate characteristics, representing a gradient from habitats having lotic characteristics to lentic habitats. All four habitat types supported mussels, but habitats most resembling unimpounded, lotic situations (relatively higher current velocity and coarser substrate) had the highest mussel abundance and species density (10.1 mussels m^?2, 1.8 species m^?2, respectively). Lentic habitats (no flow, fine substrate) were characterized by lower abundance and species density (2.0 mussels m^?2, 0.8 species m^?2, respectively), but supported mussel assemblages distinctive from lotic habitats.
• 3. Evidence of strong recent recruitment was observed for most species in the lake and was observed in all four habitat types.
• 4. Although impounded and regulated, Lower Lake represents one of the few areas of stable large‐stream habitat in the region. The presence of a diverse, healthy mussel community in this highly modified habitat suggests that a large component of the regional mussel fauna is relatively resilient and adaptable and is limited primarily by the absence of stable river reaches. Management actions that increase stream stability are likely to result in expansion of the mussel fauna and restoration of a valuable component of ecosystem function in this region.

Published in 2006 by John Wiley & Sons, Ltd.     

The local responses of aquatic ecosystems to adjacent grassland conservation: Can streams of dreams exist in a degraded riverscape?

1. Landscape homogenization and the removal of riparian areas have altered stream ecosystems worldwide. Numerous conservation programmes attempt to improve water quality and increase instream habitat heterogeneity to elicit desired biological responses. However, the effectiveness of many conservation efforts on isolated stream fragments remains unknown, especially in grassland regions.
2. The effects of grassland conservation practices and the re-establishment of riparian corridors in the James River basin, South Dakota (USA) on stream water quality, habitat availability and aquatic macroinvertebrate and fish assemblages were studied in an agriculturally dominated prairie landscape.
3. Grassland conservation efforts may have repaired riparian condition, reduced turbidity and created more diverse instream habitat complexes at conservation sites based on comparisons with paired reference reaches. Reference sites were relatively homogeneous, with prevalent siltation, bank erosion and disturbances to the riparian vegetation. Owing to significant riparian vegetation development, overhanging and aquatic vegetation, benthic detritus and woody materials were significantly more common at conservation reaches.
4. Restoration efforts that assume ‘if you (re-)build it, they will come’ (i.e. the ‘field of dreams’ hypothesis) underestimate other important barriers to biodiversity restoration in dynamic, grassland riverscapes. Although aquatic organisms in grassland ecosystems are adapted to rapidly inhabit available habitats, the development of niche space at conservation reaches did not directly result in colonization by aquatic life.
5. Grassland management actions did not address stream connectivity issues or overcome land use influences elsewhere in the riverscape that may govern the responses of aquatic macroinvertebrates and fish. Stream fragmentation and continuing, damaging land use patterns seemed to exceed the positive effects of restoring isolated stream reaches in these heavily degraded catchments. Catchment-scale management strategies that combine reach-level restoration actions with efforts to improve connectivity are likely to be more successful in degraded riverscapes.

     

Rapid response of fish and aquatic habitat to removal of a tidal barrier

1. River barrier removal is used increasingly as a conservation tool to restore lotic habitat and river connectivity, but evidence of its efficacy is incomplete. This study used a before–after methodology to determine the effects of removing a tidal-limit barrier on the fishes, macroinvertebrates, and habitats of an English coastal stream.
2. Following barrier removal, habitat diversity increased immediately upstream and remained similar downstream. Mobilized silt altered the substrate composition immediately downstream, but this was temporary as silt was flushed out the following winter. Changes to macroinvertebrate communities occurred upstream and downstream of the former barrier but these were transient.
3. A dramatic and sustained increase in fish density occurred immediately upstream of the barrier after its removal, but effects downstream were minor. The fish community upstream changed, largely due to rapid recruitment and dispersal of endangered European eel (Anguilla anguilla). Eel density in the formerly impounded zone increased from 0.5 per 100 m² before barrier removal to 32.5 per 100 m² 5 months after removal. By 17 months after barrier removal there was no difference in eel density across the six sections sampled.
4. Although resident stream fishes such as bullhead (Cottus gobio species complex, protected under the European Habitats Directive) were abundant in middle and upper-stream sections, brown trout (Salmo trutta, a listed species for biodiversity conservation in England and Wales) density remained low during the study and recruitment was poor. This suggests that although colonization access for anadromous trout was available, habitat upstream may have been unsuitable for reproduction, indicating that wider catchment management is required to complement the restoration of connectivity.
5. These findings suggest that tidal barrier removal is an effective method of restoring lotic habitats and connectivity, and can be beneficial for resident and migratory fishes including those of conservation importance (e.g. European eel) in coastal streams.

     

Forest conversion adversely affects native Macrobrachium shrimp assemblages in tropical Malaysian streams

1. Commodity-driven forest conversion represents one of the most severe threats to freshwater biodiversity in Southeast Asia, notably causing population declines and the extinction of freshwater fish species.
2. Although a variety of freshwater taxa are likely to be adversely affected by forest conversion, little is known about the impact on ecologically and economically important invertebrates such as decapod crustaceans.
3. This study evaluated the impact of forest conversion and land-use change on freshwater Macrobrachium shrimp species, using species richness, abundance, and environmental data collected from 20 streams across southern Peninsular Malaysia. Streams were located in three types of landscape: forest; oil palm plantation; and mixed land use, comprising young secondary forest, small-scale plantations, patches of open and sparsely vegetated areas, and agricultural fields and clearings.
4. Generalized linear models showed that even incomplete change from forest habitats to mixed land use and oil palm plantation resulted in significantly lower Macrobrachium native species richness and higher non-native species abundance. Native species richness was positively correlated with canopy cover, leaf litter, substrate size, and dissolved oxygen, and was negatively correlated with water temperature and conductivity. Native species richness was also negatively correlated with non-native species abundance, with non-native species abundance increasing along the human disturbance gradient.
5. These results highlight the need for riparian habitat protection to conserve native Macrobrachium and limit the spread of non-native species. A management priority should be to maintain or restore optimum instream habitat conditions for shrimps, which would also benefit fish and other benthic macroinvertebrates. Suitable riparian management requires substantial support and funding from multiple stakeholders, but it can be aligned with other catchment-based strategies to optimize the use of limited resources available for freshwater biodiversity conservation.

     

Native and introduced fish community structure in a freshwater swamp forest: Implications for conservation and management

1. Freshwater swamp forests are poorly studied but highly threatened freshwater habitats, especially in Southeast Asia. Very little is known about the environmental factors associated with the assembly and spatial distribution of fish communities in these acid‐water habitats, although such knowledge is of immense importance for conservation and management.
2. Fish assemblages in 40 stream sites throughout the Nee Soon Swamp Forest, Singapore, were surveyed using push nets from October 2013 to November 2014. The Nee Soon Swamp Forest is the last substantial remnant of freshwater swamp forest habitat in Singapore, and today it is the only refuge for many of the native forest‐specialist freshwater fish species.
3. The overall diversity and richness of the fish community are positively correlated with depth, stream order, and canopy cover, and are negatively correlated with distance to a connected reservoir, mean velocity, and silt substrate. Observed patterns indicate that three main communities exist, each with distinct associated species and environmental parameters. One is a novel community of introduced species and non‐forest specialist native species found only at the outskirts (downstream portion) of the swamp forest, close to a reservoir connection that drains the swamp, whereas the other two communities are found in the interior of the swamp forest and harbour mostly forest‐specialist native species of restricted distribution and high conservation value.
4. The community on the outskirts may be a potential route for introduced species to spread and establish populations deeper within the swamp forest. At present the native community within the swamp forest appears to be healthy, but constant monitoring is needed to ensure that the native community is not threatened by loss of habitat or introduced species.

     

Big impacts from small abstractions: The effects of surface water abstraction on freshwater fish assemblages

1. Abstractions and diversions are prevalent in river networks worldwide; however, specific mechanisms and measures reflecting changes in functional characteristics of aquatic assemblages in response to flow abstraction have not been well established. In particular, the influence of small takes on fish assemblages is poorly understood.
2. Field surveys and stable‐isotope analyses were used to evaluate the impact of differing levels of flow abstraction on fish assemblage structure, and native–non‐native patterns of coexistence, associated with small surface water abstractions in four streams in New Zealand. Study design accounted for longitudinal processes (spatial autocorrelation) to isolate the effects of abstractions on fish assemblages.
3. Reaches with reduced flows downstream of abstraction points had significantly lower fish abundances per metre of stream length, probably because of decreased habitat size, altered interspecific interactions and barriers to movement. The loss of larger fish in reaches with high abstraction resulted in shallower mass–abundance slopes and shorter stable isotope‐derived food‐chain lengths, likely to have been caused by fewer trophic links in the food web. The large fish absent from these reaches were flow‐sensitive introduced salmonids, resulting in higher relative abundances of small‐bodied native fish, probably as a result of predatory and competitive release.
4. Quantification of metrics designed to characterize ecosystem functioning as well as abundance and species composition indicated that small water abstractions can alter both the structure and composition of stream fish assemblages and modify the outcomes of native–non‐native species interactions. Thus, a better understanding of the effects of small abstractions could be used to improve the strategic management of fish in invaded riverscapes.

     

Land cover,riparian zones and instream habitat influence stream fish assemblages in the eastern Amazon

The Amazon rainforest has experienced rapid land‐use changes over the last few decades, including extensive deforestation that can affect riparian habitats and streams. The aim of this study was to assess responses of stream fish assemblages to deforestation and land cover change in the eastern Amazon. We expected that percentage of forest in the catchment is correlated with local habitat complexity, which in turn determines fish assemblage composition and structure. We sampled 71 streams in areas with different land uses and tested for relationships between stream fish assemblages and local habitat and landscape variables while controlling for the effect of intersite distance. Fish assemblage composition and structure were correlated with forest coverage, but local habitat variables explained more of the variation in both assemblage composition and structure than landscape variables. Intersite distance contributed to variance explained by local habitat and landscape variables, and the percentage of variance explained by the unique contribution of local habitat was approximately equivalent to the shared variance explained by all three factors in the model. In these streams of the eastern Amazon, fish assemblages were most strongly influenced by features of instream and riparian habitats, yet indirect effects of deforestation on fish assemblage composition and structure were observed even though intact riparian zones were present at most sites. Long‐term monitoring of the hydrographic basin, instream habitat and aquatic fauna is needed to test for potential legacy effects and time lags, as well as assess species responses to continuing deforestation and land‐use changes in the Amazon.     

Country‐wide analysis of large wood as a driver of fish abundance in Swedish streams: Which species benefit and where?

1. Rivers are heavily affected by human impacts that threaten many fish species. Among restoration measures, the addition of large wood (LW) in streams has been shown to increase fish abundance, yet which species benefit from LW, to what extent relative to other drivers, and which factors influence LW quantity is not clear, and these uncertainties limit our ability to use LW as an effective restoration measure.
2. Here, a time series (from 1993 to 2016) of electrofishing data, including 3641 streams across Sweden, was used to investigate the beneficial effects of LW on the abundance of juvenile brown trout, Salmo trutta, juvenile Atlantic salmon, Salmo salar, and juvenile and adult sculpins, Cottus gobio and Cottus poecilopus, while accounting for other abiotic and biotic factors, and the drivers of LW abundance at a country‐wide scale.
3. Large wood benefitted brown trout, and the effects were greater with decreasing shaded stream surface. LW effects were comparable in magnitude to the positive effects of average annual air temperature and the negative effects of stream depth and predator abundance – factors where the influence was second only to the negative effects of stream width. LW did not benefit salmon abundance, which was correlated positively with stream width and negatively with altitude, nor did it benefit sculpin abundances, which mainly decreased with annual average air temperature and altitude.
4. The quantity of LW strongly diminished with stream width, and, to a lesser extent, with stream depth, altitude, annual average air temperature, and forest age, whereas it increased with stream velocity, slope, and forest cover.
5. The results suggest that LW can be used as an effective restoration tool for brown trout in shallow and narrow streams, especially in areas with little shade. Here, the addition of LW may help to alleviate the impacts of forest clearance and climate change.

     

Riverine spawning,long distance larval drift,and floodplain recruitment of a pelagophilic fish: A case study of golden perch (Macquaria ambigua) in the arid Darling River,Australia

1. Pelagic spawning riverine fish (pelagophils) spawn in free‐flowing river habitats with downstream drift of eggs and larvae but the spatial scale is often unknown, and this constitutes a major ecological knowledge gap.
2. In the arid Darling River in south‐eastern Australia, the present objectives were: (i) to determine the potential downstream dispersal distance of young golden perch (Macquaria ambigua); and (ii) to evaluate whether provision of environmental water enhanced dispersal of young fish from Menindee Lakes to the lower Darling River (LDR) while also cueing further spawning in downstream lotic reaches.
3. Golden perch spawned in unregulated lotic tributaries on a flood pulse and larvae drifted or dispersed >1,600 km downstream and entered large ephemeral productive floodplain lake nursery habitats as fully scaled fingerlings.
4. Planned releases of environmental water cued golden perch spawning in the LDR and enabled juvenile fish to disperse downstream from the Menindee Lakes nursery into receiving populations in the LDR, Great Darling Anabranch, and southern Murray River, with some fish potentially completing an active migration of >2,100 km by age 1 year.
5. The Darling River case study highlights the need for a system‐scale approach to the conservation management of pelagophilic fish, along with multi‐year perennial flow strategies to improve ecosystem integrity in large rivers globally.

     

Impacts of Indian waterfern (Ceratopteris thalictroides (L.) Brongn.) infestation and removal on macroinvertebrate biodiversity and conservation in spring‐fed streams in the Australian arid zone

相似文献   

Beaver dams shift desert fish assemblages toward dominance by non‐native species (Verde River,Arizona, USA)

The reintroduction of beaver (Castor canadensis) into arid and semi‐arid rivers is receiving increasing management and conservation attention in recent years, yet very little is known about native versus non‐native fish occupancy in beaver pond habitats. Streams of the American Southwest support a highly endemic, highly endangered native fish fauna and abundant non‐native fishes, and here we investigated the hypothesis that beaver ponds in this region may lead to fish assemblages dominated by non‐native species that favour slower‐water habitat. We sampled fish assemblages within beaver ponds and within unimpounded lotic stream reaches in the mainstem and in tributaries of the free‐flowing upper Verde River, Arizona, USA. Non‐native fishes consistently outnumbered native species, and this dominance was greater in pond than in lotic assemblages. Few native species were recorded within ponds. Multivariate analysis indicated that fish assemblages in beaver ponds were distinct from those in lotic reaches, in both mainstem and tributary locations. Individual species driving this distinction included abundant non‐native green sunfish (Lepomis cyanellus) and western mosquitofish (Gambusia affinis) in pond sites, and native desert sucker (Catostomus clarkii) in lotic sites. Overall, this study provides the first evidence that, relative to unimpounded lotic habitat, beaver ponds in arid and semi‐arid rivers support abundant non‐native fishes; these ponds could thus serve as important non‐native source areas and negatively impact co‐occurring native fish populations.     

Restricted movement of prairie fishes in fragmented riverscapes risks ecosystem structure being ratcheted downstream

1. Prairie streams are dynamic systems in which habitat patches are sporadically created and lost during extreme hydrological events. The persistence of fish species depends on life‐history traits that facilitate their widespread dispersal to recolonize habitats after stochastic extirpation. Artificial barriers are thought to reduce recolonization opportunities and to ultimately displace populations downstream, but the ecological consequences of lost diversity above the barriers are largely unknown.
2. The susceptibility of four prairie fishes to fragmentation and the consequent risk to stream ecosystem processes are described. The selected species exhibit wide tolerances to environmental stressors, represent unique functional feeding guilds, and have different habitat affinities.
3. The ability of each species to access (jumping ability) and successfully traverse (swimming endurance) simulated instream barriers was quantified in the laboratory. Experimental stream complexes were used to isolate the effects of these species on ecosystem structure and function. These replicated single‐species experiments were compared with ‘no fish’ controls to identify the ecological role of each.
4. Small vertical barriers blocked most passage, and with open access all species were unable to traverse relatively short distances against modest water velocities. Stream fragmentation will alter headwater fish assemblage structure and promote the most mobile species. Each species had slightly different effects on the stream ecosystem structure resulting from their different habitat preferences and diets.
5. Without colonization opportunities from neighbouring populations, disturbance events will alter headwater fish assemblages and may degrade the ecosystem structure above barriers.
6. Fragmented riverscapes interact with harsh disturbance regimes to form an ecological ratchet. Systematic species loss above barriers outweighs the opportunity for improvement, suggesting that ecosystem structure may be moving downstream.

     

Can a cow save a newt? The role of cattle drinking troughs in amphibian conservation

1. Amphibians are the vertebrate group experiencing the steepest global population decline and species loss. Habitat alteration and loss caused by the intensification of agriculture is among the main causes; however, in the past, amphibians have been favoured by traditional agriculture and husbandry as more terrestrial and aquatic habitats became available through land‐use diversification and the construction of artificial facilities for cattle watering. Troughs for cattle watering may represent the only permanent water points for amphibian reproduction in human‐modified landscapes.
2. The present study focused on Lissotriton vulgaris meridionalis, a semi‐aquatic salamander, subendemic and widespread in Italy, capable of colonizing artificial aquatic habitats. The main goal was to determine the importance of drinking troughs for the ecology and conservation of the species in a hilly area (Latium region, Central Italy) subjected to traditional livestock farming (i.e. Maremmana cattle).
3. Specifically, generalized linear models (GLMs) were used to analyse the effects of drinking trough characteristics (i.e. size, substrate, aquatic vegetation), landscape features (distance to the forest, forest cover, percentage of cultivated lands and infrastructural development, terrestrial connectivity) and intensity of management practices on the occurrence and abundance of the target species.
4. In the light of the present results, it is suggested that drinking troughs represent suitable surrogates for pristine habitats for L. vulgaris meridionalis. Hence, even man‐made aquatic habitats, associated with traditional husbandry, may help to sustain amphibian populations in landscapes where natural wetlands are scarce. The present findings are timely because of the lack of empirical data on the role of drinking troughs in amphibian conservation within rural socio‐economic scenarios, which may have been neglected in research and policy in favour of lakes, rivers and streams.

     

It is the ambience,not the menu. Prey availability does not drive habitat selection by the endangered Pyrenean desman

1. The Pyrenean desman (Galemys pyrenaicus) is an endangered stream-dwelling insectivore endemic to the Iberian Peninsula and the north of the Pyrenees. It favours riffles over slow habitats such as runs or pools, yet it is still unclear whether habitat preference is based on prey availability or on other factors, such as mechanical constraints on its hunting habits.
2. Desman diet and prey selection were analysed along the pristine Elama Stream and the slightly modified Leitzaran Stream in the Basque Country, Spain.
3. In each stream the prey consumed were identified by metabarcoding 94 desman faeces, and prey availability characterized from 10 Surber samples taken in each habitat type (riffles, runs and pools). Invertebrates were sorted and identified, the biomass of each taxon was calculated, and their DNA was also extracted, amplified using PCR, and sequenced to build a reference database.
4. Prey availability and diet varied between streams. Desmans positively selected shredders and invertebrates that live on the substrate, and selected against taxa that live in fine sediment, taxa with hard shells or those that are highly mobile. The diet of desmans was more selective in the Elama, the stream with better ecological status. Food availability did not differ among habitats, and therefore does not explain the preference of desmans for riffles; rather, mechanical constraints to deal with buoyancy and physical habitat heterogeneity were hypothesized to be the reason behind the habitat preference.
5. The results suggest that promoting the formation of riffles in streams can improve the situation of some desman populations living in degraded habitats.

     

The importance of ecosystem‐based management for conserving aquatic migratory pathways on tropical high islands: a case study from Fiji

• 1. Tropical, high islands of the Pacific have developed unique freshwater fish faunas that are currently threatened by a range of human activities. This paper documents distinct differences in life history strategies from fish communities found in streams of Fiji compared with fish assemblages in freshwater systems on larger continental land masses. While river systems of northern Australia and Papua New Guinea have a high proportion of freshwater residents, the Fiji fauna is dominated by amphidromous gobiids that migrate across a broad range of habitats throughout their life cycle.
• 2. The number of amphidromous fish species and the number of all fish species in mid‐reaches of Fiji rivers are significantly affected by loss of catchment forest cover and introductions of tilapia (Oreochromis spp.). On average, stream networks with established Oreochromis spp. populations have 11 fewer species of native fish than do intact systems. The fish that disappear are mostly eleotrid and gobiid taxa, which have important dietary and economic value.
• 3. Based on the strong links between catchment land clearing, non‐native species introductions and loss of migratory pathways for freshwater fish, spatial information was compiled on a national scale to identify priority areas for conservation in Fiji with intact connectivity between forests, hydrologic networks and coral reefs. Areas with high connectivity included remote, largely undeveloped regions of Vanua Levu (Kubulau, Wainunu, Dama, Udu Point, Natewa, Qelewara) and Taveuni, as well as smaller mapping units (Naikorokoro, Sawakasa) of Viti Levu with low density of roads and high relative amounts of mangroves and reefs.
• 4. These priority areas for conservation can only be effectively protected and managed through cross‐sectoral collaboration and ecosystem‐based approaches. Copyright © 2009 John Wiley & Sons, Ltd.